1. Field of the Invention
This invention pertains to a portable computing device. More specifically, embodiments of this invention provide for detecting and/or determining a type of an accessory device connected to a portable computing device.
2. Description of the Related Art
Portable computers such as laptop and handheld computers may be provided with additional capabilities through the use of accessory devices. The accessory devices may electrically couple to a processor of the portable computer to provide communication capabilities and external power. Accessory devices in general have been used to add functions and resources to portable computers to compensate for inherent limitations arising from their size and mobility. Previous accessory devices have been used to provide, among other things, an alternating current (A/C) supply, serial and parallel ports, modems, additional memory, and universal serial ports. The portable computer may use accessory devices to communicate with larger computers and data networks.
Portable computers are typically equipped with a time-out feature that turns the computer off after a predetermined duration of inactivity. The time-out feature is designed to preserve battery life. While the time-out feature may be necessary when the portable computer is operating from an internal battery source, accessory devices may supply an A/C converter to the portable computer to eliminate the need for the time-out feature. However, previous portable computers provide for the time-out feature to be enabled so that the portable computer switches off after a period of inactivity, even if the accessory device is supplying external power. Still, other portable computers, such as Zaurus™ personal digital assistant manufactured by the Sharp Corp. and PalmPilot™ organizers manufactured by the 3Com Corp., disable the time-out feature only when an A/C power adapter is supplied to a power terminal of the portable computer.
These devices do not disable the time-out feature when an accessory device such as a communication cradle is connected to the portable computer through a communications port. In such instances, the time-out feature can be limiting and a nuisance to the user by precluding, for example, use of programs that require minimal user interaction. Therefore, there is a need for enabling the portable computer to detect whether an accessory device supplying external power is actively connected to the portable computer.
Furthermore, a number of different types of accessories are available for use with portable computers. However, previous portable computers are not equipped to automatically determine the type of accessory device that is actively connected to the portable computer. Without this ability, the user is required to perform additional software functions to identify the particular accessory device for the portable computer. In addition, the portable computer may accidentally execute an application for an accessory device other than the one being used. In certain applications, this can be harmful to the portable computer and/or the accessory device. For example, the PalmPilot III™ may access a modem accessory device by executing a software application configured only for modem devices. In some instances, the software application may be damaging if the accessory device connected to the portable computer is erroneously identified as a modem device. Therefore, there is a need for enabling the portable computer to automatically determine the type of the accessory actively connected to it.
These and other shortcomings of previous portable computers will be addressed by various embodiments of this invention.